wrote:
What would be the ideal configuration for an aircraft engine, given
contemporary technology?

1. Start at 0 degrees F with no fuss?
Although I have never tried to start my Lycoming 0360 at that
temperature, it may very well start just fine. With expensive aircraft
engines there is just too much wear with cold starts to do it. Get a
preheat. Which leads to installed preheat devices and perhaps a
pre-oiler
2. Water cooling for dependable cabin heat?
There is actually plenty of heat available from air cooled if they
would just deliver it. A FAN would be a terrific new age idea.
3. Automatic mixture control for altitude & power?
With automation comes complexity. Personally I see no reason to
automate this. How hard is it to lean to a temperature. All you need is
a digital EGT.
4. Automatic timing control?
Great idea along with electronic ignition making hotter spark
(capacitive discharge). Actually available from Unison now as an STC.
5. Jet fuel (availability)?
I'll stick with gas, thanks. You can get it at out of the way airports.
6. Piston (for economy)?
7. Choice of RPM at cruise for same power?
Constant speed prop does just that.

I believe that delivering brand new airplanes with 1940s engines
makes
no sense whatever.
Well, it actually does. Although water cooling would allow closer
tolerences and more power, you would have to have geared engine to prop
because you need higher rpm to get the power. Again more complexity and
more weight. Probably not worth it. One thing about the existing
Lycosaurs and Contibrasaurus engines is they are simple. No emissions
stuff, simple mechanical fuel injection or carburetion, simple
mechanical magnetos. This all makes for reliability. These engines are
really all that bad. And they are light. If you look at car engines,
they are heavier for given horsepower. And one thing we definitely
don't need is heavier engines. Even though water cooling (or active
oil cooling) would make more horsepower, I wonder if after the weight
is considered if it would make more horsepower per pound of engine,
which really is the key factor. That and reliability.

A fancy engine that quits or gives trouble with high maintenance is not
an improvement. My Lycoming 0-360 has 2150 hours on it and has never
needed service. Never even had the valve covers off. I have had to
replace accessories. This is actually fairly typical if you do the oil
changes and are careful about how you start and run the engine.

Much to our modern technology chagrin, the designers of these engines
got a lot of things right. They work pretty damn well.